Identifying preoperative radiographic metrics to guide surgical selection in lumbar spondylolisthesis and stenosis.

Background Context: "Instability" often drives the decision to add fusion to decompression, yet most instability criteria lean solely on sagittal translation and have never been rigorously validated. The potential of a metric for sagittal plane translation to help decide whether fusion should be added to decompression surgery for symptomatic lumbar stenosis with spondylolisthesis was recently reported. Building on imaging and outcomes from that study, we investigated whether other motion metrics may help to predict postoperative disability and patient-reported outcomes in lumbar stenosis with spondylolisthesis. Methods: Radiographic metrics were retrospectively calculated from the prospectively collected flexion-extension radiographs of 61 patients with lumbar spinal stenosis and spondylolisthesis. A threshold-limit graphical approach was used to identify metrics and thresholds predictive of the Oswestry Disability Index, leg/buttock pain, and patient satisfaction. Outcomes were compared across groups defined by these threshold levels using statistical analysis. Results: Decompression-only surgery was associated with poorer outcomes in patients exhibiting vertical instability or significant spondylolisthesis changes between flexion and extension. Conversely, decompression-plus-fusion surgery yielded worse outcomes in cases without substantial dynamic spondylolisthesis. Conclusions: A broader definition of spinal instability may be needed when deciding whether to include fusion in treating lumbar stenosis with spondylolisthesis. Preoperative vertical instability and dynamic slip may be important in addition to translational instability. Larger prospective studies are warranted, but these metrics could help guide the decision on whether fusion is necessary and likely to improve outcomes for a common spinal disorder.